1. Field of the Invention
The present invention relates to a method for obtaining an optically active isomer of 3-chloro-2-methyl-1,2-propanediol from an enantiomeric mixture of 3-chloro-2-methyl-1,2-propanediol by taking advantage of a microorganism.
2. Description of the Related Art
Optically active isomers of 3-chloro-2-methyl-1,2-propanediol are very important and useful compounds in the production of pharmaceuticals, agrichemicals, physiologically active substances, and like optically active compounds. For example, a tertiary methyl carbinol derivative obtained from (S)-3-chloro-2-methyl-1,2-propanediol according to the method disclosed in Japanese Patent No. 2567430 is for use as a production intermediate for d-α-tocopherol (natural vitamin E). A hydroquinone derivative obtained from (R)-3-chloro-2-methyl-1,2-propanediol according to the method disclosed in Japanese Patent No. 2557068 is of use as a production intermediate for d-α-tocopherol.
Therefore, a method for efficiently obtaining optically active 3-chloro-2-methyl-1,2-propanediol is required.
Examples of methods for obtaining optically active 1,2-diol are:    (1) letting a microorganism act on a racemic 3-halogeno-1,2-propanediol to give an optically active 3-halogeno-1,2-propanediol (Japanese Unexamined Patent Publication Nos. 1988-251098 and 1994-209781);    (2) letting a microorganism act on racemic 1,2-propanediol to give optically active 1,2-propanediol (Japanese Unexamined Patent Publication No. 1994-30709); and    (3) use of a cobalt salen catalyst to give optically active 1,2-propanediol (Science 1997, 277, 936-938). These publications, however, are silent as to optically active 3-chloro-2-methyl-1,2-propanediol.
A known method for producing an optically active 3-chloro-2-methyl-1,2-propanediol isomer is by a chemical synthesis using an optically active tartaric acid ester (Japanese Patent No. 2567430). The method disclosed therein requires expensive ingredients and a low-temperature (−18° C.) reaction and takes a long period of time to complete, therefore being impractical. In comparison, a reaction using a microorganism could presumably be carried out under mild conditions without expensive ingredients.
As examples of microorganisms that can produce optically active alcohols, Pseudomonas sp. DS-K-436-1 is described as having an ability to stereoselectively dehalogenate (R)-4-halogeno-1,3-butanediol in Japanese Unexamined Patent Publication No. 2001-120296, and Pseudomonas sp. OS-K-29 is described as having an ability to assimilate (R)-2,3-dibromo-1-propanol in Japanese Examined Patent Publication No. 1989-51999. Moreover, Pseudomonas sp. DS-SI-5, Pseudomonas nitroreducens DS-S-RP8 and Alcaligenes sp. DS-S-7G are described as having an ability to assimilate (R)-3-halogeno-1,2-propanediol or (S)-1,2-propanediol in Japanese Unexamined Patent Publication Nos. 1991-191795, 2001-149090 and 2002-253295.
However, the microorganisms disclosed in Japanese Unexamined Patent Publication Nos. 2001-120296, 1991-191795, 2001-149090 and 2002-253295 and Japanese Examined Patent Publication No. 1989-51999 are described as usable in the production of just optically active secondary alcohols. These publications do not discuss the production of a tertiary alcohol, e.g., 3-chloro-2-methyl-1,2-propanediol, using the aforementioned microorganisms.
In Japanese Unexamined Patent Publication No. 1991-191794, Pseudomonas sp. DS-K-2D1 is described as having an ability to assimilate a secondary alcohol, i.e., a (S)-3-halogeno-1,2-propanediol, while sustaining the (R)-3-halogeno-1,2-propanediol. However, this microorganism does not have an ability to sustain an optically active isomer of 3-chloro-2-methyl-1,2-propanediol within an enantiomeric mixture of a tertiary alcohol, i.e., 3-chloro-2-methyl-1,2-propanediol.
As described above, microorganisms that can stereoselectively resolve secondary alcohols do not necessarily have an ability to stereoselectively resolve tertiary alcohols.
A practical method for inexpensively obtaining optically active 3-chloro-2-methyl-1,2-propanediol in large amounts has been heretofore unknown.